1. Field of the Invention
The present invention relates to a cache memory system, and specifically, to an updating method and an updating program for a cache memory system.
2. Description of the Related Art
Cache memories currently used in a microprocessor and the like, in which address translation information and data are stored, are configured to store a plurality of sets of information that is a part of the information stored in a main memory. A cache memory storing the address translation information is referred to as an address cache or a Translation Look-aside Buffer (TLB). A cache memory storing data is referred to as a data cache. A storage area stores a set of information data. Such data is simply referred to as “entry.” The cache memories themselves cannot store all the information required by a CPU of a computer system. Therefore, it is necessary to fetch new information data from a main memory and update the cache memories with the new information.
There are various methods for storing the address translation information of the TLB or the data cache in the cache memory itself and for utilizing the TLB or the data cache. As for a cache memory that is fully associative, a method for randomly selecting an entry data is employed in order to prevent a complex circuit design.
However, in terms of frequency of usage, same data entries that are less frequently used should be updated in each set of entry information in a cache memory. On the other hand, it is inappropriate to update some entries because they are more frequently used. The method for randomly selecting an entry raises the possibility that the more frequently used entries are updated.
Thus, the entry information that has been updated must be reregistered. As a result of reregistering entry information, time efficiency is reduced and performance is degraded.
In the case of a fully associative cache memory, the random entry method is used to select an entry to be updated, so as to avoid a complicated circuit design. Accordingly, there is a possibility that a more frequently used entry is updated.